1. Turbo-molecular pumps in magnetic fields (Visit to Karlsruhe Institute of Technology) Vishal Francis, Tom Weston 17/10/2012

2. Motivation Rotor heating Shielding Experimental setup How can MICE benefit? Vishal Francis, Tom Weston 17/10/2012

3. To discuss published paper with Joachim Wolf See experimental setup Meet Alexander Jansen, Ph.D “Modelling rotor temperature (TMP), in magnetic fields. Motivation Vishal Francis, Tom Weston 17/10/2012

4. Work at KIT Sheet from J. Wolf presentation KATRIN: – differential pumping sections (2 - 18mT)  shielding – spectrometer (save distance of TMPs ?) Nuclear fusion plant (JET, ITER, …) – pulsed mag. field (>> 5 mT) Operation of TMPs in magnetic fields – magnetic fields induce eddy currents in the rotor  rotor temperature ?  overheating leads to destruction of the pump ! – stable operation:  rotation frequency ?  magnetic bearing ? – influence of the direction of the field ? – effect of shielding ? KATRIN: – differential pumping sections (2 - 18mT)  shielding – spectrometer (save distance of TMPs ?) Nuclear fusion plant (JET, ITER, …) – pulsed mag. field (>> 5 mT) Operation of TMPs in magnetic fields – magnetic fields induce eddy currents in the rotor  rotor temperature ?  overheating leads to destruction of the pump ! – stable operation:  rotation frequency ?  magnetic bearing ? – influence of the direction of the field ? – effect of shielding ? J. Wolf: Turbo-molecular pumps in magnetic fields 21.07.2011 Vishal Francis, Tom Weston 17/10/2012

5. Rotor Heating Vishal Francis, Tom Weston 17/10/2012

7. Reduction of the field by shielding shieldingshielding shielded partly shielded !!! unshielded unshieldedunshielded B · sin(φ) φ J. Wolf: Turbo-molecular pumps in magnetic fields 21.07.2011 no eddy currents for homogeneous field no eddy currents for homogeneous field eddy currents for external field eddy currents for external field SHIELDING Vishal Francis, Tom Weston 17/10/2012

8. Experimental setup fore-vacuum (S eff  7 l/s) fore-vacuum rotor temperature stability of the magnetic bearing rotation frequency rotor temperature stability of the magnetic bearing rotation frequency J. Wolf: Turbo-molecular pumps in magnetic fields 21.07.2011 PT100sensorPT100sensor PyrometerPyrometer Helmholtz coils (  = 120 cm) Helmholtz coils (  = 120 cm) TMPTMP Vishal Francis, Tom Weston 17/10/2012

9. Reminder Region of uniform magnetic field where TMP will sit

10. Helmholtz coils Helmholtz coils tested with 3D sensor Inner volume scanned Calibration with external Hall probe Test of homogeneity of B-field: ±1% Helmholtz coils tested with 3D sensor Inner volume scanned Calibration with external Hall probe Test of homogeneity of B-field: ±1% Helmholtz coils Hall probe y z x y z coils 1.2 m radius of rotor thesis by Stefan Zepter J. Wolf: Turbo-molecular pumps in magnetic fields 21.07.2011 Vishal Francis, Tom Weston 17/10/2012

11. Test setup summary Coil diameter 1.2m, Field up to 200G long term, can test 500G short term. Test TMP - long term tests, Quick shielding test, using hall probes and shield set up, Quick electronic equipment test, Vishal Francis, Tom Weston 17/10/2012

12. How can this help MICE We can use the set up at KIT. (We will have to request and send a proposal for costing). We can do quick tests using staff and students at KIT (helps their Ph.D). Electronic items???, magnetic shields and control equipment etc. Long term TMP tests (may need our staff to assist). Vishal Francis, Tom Weston 17/10/2012

13. What next? Invite Joachim Wolf and Alexander Jansen to RAL (To talk to MICE. A good source for consultation) Do we make a test setup at RAL or use the facility at KIT? Other MICE groups converge and propose a “test wish list”. Vishal Francis, Tom Weston 17/10/2012